Power steering gear with variable rate torsion bar for optimized steering

Abstract

Vehicle power steering gear with a torsion bar whose stiffness is adjusted by an axially shiftable nut that provides a movable gripping point for one end of the torsion bar whose position determines the pliable length of the bar and the steering effort required to steer the vehicle.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. In a vehicle, a power steering gear providing power steering assist effort comprising a housing, an input shaft mounted for turning movement in said housing in response to steering effort by a vehicle operator, output gearing operatively mounted for turning movement in said housing and having output means extending outward from said housing, hydraulic power actuator means operatively mounted in said housing for moving said output means, rotary valve means in said housing operatively connected to a source of pressurized hydraulic fluid for selectively supplying and exhausting pressurized fluid to and from said actuator means to effect the hydraulic power movement of said actuator means and said output means, said valve means comprising a valve body member drivingly connected to said output gearing and a valve spool member connected to said input shelf, lost motion connector means operatively connecting said output gearing to said valve spool member and thereby to said input shaft to permit the vehicle operator to mechanically move said actuator means in said housing, elongated torsion bar means having an outer end portion and an inner end, said torsion bar means extending into said input shaft and operatively connected to said output gearing and to said input shaft to provide a centering spring interconnection between said valve body member and said valve spool member, fixed retainer means for securing said inner end of said torsion bar means to said output gearing and axially shiftable retainer means axially spaced from said retainer means for securing said outer end portion of said torsion bar means to said input shaft at any selected one of a plurality of positions spaced from said innner end of said torsion bar to thereby control the effective torsion bar length and stiffness so that manual steering effort can be variably set between maximum effort at minimum spacing and minimum effort at maximum spacing and operator means extending into said valve spool for moving said shiftable retainer means. 
     
     
       2. In a vehicle, a power steering gear providing power steering assist effort comprising a housing, an input shaft mounted for turning movement in said housing in response to steering effort by a vehicle operator, output gearing operatively mounted for turning movement in said housing and having output means extending outward from said housing, hydraulically powered actuator means operatively mounted in said housing for moving said output means, rotary valve means in said housing operatively connected to a source of pressurized hydraulic fluid for selectively suppplying and exhausting pressurized fluid to and from said actuator means to effect the hydraulic powered movement of said actuator means and said output means, said valve means comprising a valve body member drivingly connected to said output gearing and a valve spool member connected to said input shaft, lost motion connector means operatively connecting said output gearing to said valve spool member and thereby to said input shaft to permit the vehicle operator to mechanically move said actuator means in said housing, elongated torsion bar means having an inner end and an outer end portion and extending into said input shaft and operatively connected to said output gearing and to said shaft to provide a contering spring connnection between said valve body and said valve spool members, fixed retainer means for securing said inner end of said torsion bar means to said output gearing and axially shiftable retainer means axially spaced from said fixed retainer means operatively interconnnecting said outer end portion of said torsion bar means and said input shaft at selected positions spaced from said fixed retainer means so that the spring rate of said torsion bar can be changed by the vehicle operator to provide manual steering at vehicle highway speeds and maximum power steering at low vehicle speeds and when parking the vehicle. 
     
     
       3. In a vehicle, a power steering gear providing power steering assist effort comprising a housing, an input shaft mounted for turning movement in said housing in response to steering effort by a vehicle operator, output gearing operatively mounted for turning movement in said housing and having output means extending outward from said housing, hydraulically power actuator means operatively mounted in said housing for moving said output means, rotary valve means in said housing operatively connected to a source of pressurized hydraulic fluid for selectively supplying and exhausting pressurized fluid to and from said actuator means to effect the hydraulic powered movement of said actuator means and said output means, said valve means comprising a valve body memeber drivingly connected to said output gearing and a valve spool member connected to said input shaft, lost motion connector means operatively connecting said output gearing to said valve spool member and thereby to said input shaft to permit the vehicle operator to mechanically move said actuator means in said housing, elongated torsion bar means having an inner end and an outer end portion extending into said input shaft and operatively connected to said output gearing and to said input shaft to provide a centering spring connection between said valve body member and said valve spool member, fixed retainer means for securing said inner end of said torsion bar means to said output gearing and axially shiftable nut means axially spaced from said fixed retainer means and slidably connected to said torsion bar means and said input shaft for securing said outer end portion of torsion bar means to said input shaft at selected positions from said inner end of said torsion bar to thereby control the effective torsion bar length and stiffness so that manual steering effort can be variably set between maximum effort at minimum spacing and minimum effort at maximum spacing and elongated operator means extending into said valve spool means and operatively connected to said nut means for shifting said nut means.